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/*
* Nyberg-Rueppel
* (C) 1999-2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/pk_utils.h>
#include <botan/nr.h>
#include <botan/keypair.h>
#include <botan/reducer.h>
#include <future>
namespace Botan {
NR_PublicKey::NR_PublicKey(const AlgorithmIdentifier& alg_id,
const secure_vector<byte>& key_bits) :
DL_Scheme_PublicKey(alg_id, key_bits, DL_Group::ANSI_X9_57)
{
}
/*
* NR_PublicKey Constructor
*/
NR_PublicKey::NR_PublicKey(const DL_Group& grp, const BigInt& y1)
{
group = grp;
y = y1;
}
/*
* Create a NR private key
*/
NR_PrivateKey::NR_PrivateKey(RandomNumberGenerator& rng,
const DL_Group& grp,
const BigInt& x_arg)
{
group = grp;
x = x_arg;
if(x == 0)
x = BigInt::random_integer(rng, 2, group_q() - 1);
y = power_mod(group_g(), x, group_p());
if(x_arg == 0)
gen_check(rng);
else
load_check(rng);
}
NR_PrivateKey::NR_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<byte>& key_bits,
RandomNumberGenerator& rng) :
DL_Scheme_PrivateKey(alg_id, key_bits, DL_Group::ANSI_X9_57)
{
y = power_mod(group_g(), x, group_p());
load_check(rng);
}
/*
* Check Private Nyberg-Rueppel Parameters
*/
bool NR_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
{
if(!DL_Scheme_PrivateKey::check_key(rng, strong) || x >= group_q())
return false;
if(!strong)
return true;
return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-1)");
}
namespace {
/**
* Nyberg-Rueppel signature operation
*/
class NR_Signature_Operation : public PK_Ops::Signature_with_EMSA
{
public:
typedef NR_PrivateKey Key_Type;
NR_Signature_Operation(const NR_PrivateKey& nr, const std::string& emsa) :
PK_Ops::Signature_with_EMSA(emsa),
q(nr.group_q()),
x(nr.get_x()),
powermod_g_p(nr.group_g(), nr.group_p()),
mod_q(nr.group_q())
{
}
size_t message_parts() const override { return 2; }
size_t message_part_size() const override { return q.bytes(); }
size_t max_input_bits() const override { return (q.bits() - 1); }
secure_vector<byte> raw_sign(const byte msg[], size_t msg_len,
RandomNumberGenerator& rng) override;
private:
const BigInt& q;
const BigInt& x;
Fixed_Base_Power_Mod powermod_g_p;
Modular_Reducer mod_q;
};
secure_vector<byte>
NR_Signature_Operation::raw_sign(const byte msg[], size_t msg_len,
RandomNumberGenerator& rng)
{
rng.add_entropy(msg, msg_len);
BigInt f(msg, msg_len);
if(f >= q)
throw Invalid_Argument("NR_Signature_Operation: Input is out of range");
BigInt c, d;
while(c == 0)
{
BigInt k;
do
k.randomize(rng, q.bits());
while(k >= q);
c = mod_q.reduce(powermod_g_p(k) + f);
d = mod_q.reduce(k - x * c);
}
secure_vector<byte> output(2*q.bytes());
c.binary_encode(&output[output.size() / 2 - c.bytes()]);
d.binary_encode(&output[output.size() - d.bytes()]);
return output;
}
/**
* Nyberg-Rueppel verification operation
*/
class NR_Verification_Operation : public PK_Ops::Verification_with_EMSA
{
public:
typedef NR_PublicKey Key_Type;
NR_Verification_Operation(const NR_PublicKey& nr, const std::string& emsa) :
PK_Ops::Verification_with_EMSA(emsa),
q(nr.group_q()), y(nr.get_y())
{
powermod_g_p = Fixed_Base_Power_Mod(nr.group_g(), nr.group_p());
powermod_y_p = Fixed_Base_Power_Mod(y, nr.group_p());
mod_p = Modular_Reducer(nr.group_p());
mod_q = Modular_Reducer(nr.group_q());
}
size_t message_parts() const override { return 2; }
size_t message_part_size() const override { return q.bytes(); }
size_t max_input_bits() const override { return (q.bits() - 1); }
bool with_recovery() const override { return true; }
secure_vector<byte> verify_mr(const byte msg[], size_t msg_len) override;
private:
const BigInt& q;
const BigInt& y;
Fixed_Base_Power_Mod powermod_g_p, powermod_y_p;
Modular_Reducer mod_p, mod_q;
};
secure_vector<byte>
NR_Verification_Operation::verify_mr(const byte msg[], size_t msg_len)
{
const BigInt& q = mod_q.get_modulus();
if(msg_len != 2*q.bytes())
throw Invalid_Argument("NR verification: Invalid signature");
BigInt c(msg, q.bytes());
BigInt d(msg + q.bytes(), q.bytes());
if(c.is_zero() || c >= q || d >= q)
throw Invalid_Argument("NR verification: Invalid signature");
auto future_y_c = std::async(std::launch::async, powermod_y_p, c);
BigInt g_d = powermod_g_p(d);
BigInt i = mod_p.multiply(g_d, future_y_c.get());
return BigInt::encode_locked(mod_q.reduce(c - i));
}
}
BOTAN_REGISTER_PK_SIGNATURE_OP("NR", NR_Signature_Operation);
BOTAN_REGISTER_PK_VERIFY_OP("NR", NR_Verification_Operation);
}
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